Github user marmbrus commented on a diff in the pull request:
https://github.com/apache/spark/pull/8909#discussion_r41421569
--- Diff: sql/core/src/main/scala/org/apache/spark/sql/SQLContext.scala ---
@@ -1208,36 +1204,72 @@ object SQLContext {
private val INSTANTIATION_LOCK = new Object()
/**
- * Reference to the last created SQLContext.
+ * The active SQLContext for threads.
+ */
+ private val activeContexts: InheritableThreadLocal[SQLContext] =
+ new InheritableThreadLocal[SQLContext]
+
+ /**
+ * Reference to the created SQLContext.
*/
- @transient private val lastInstantiatedContext = new
AtomicReference[SQLContext]()
+ @transient private val instantiatedContext = new
AtomicReference[SQLContext]()
/**
* Get the singleton SQLContext if it exists or create a new one using
the given SparkContext.
+ *
* This function can be used to create a singleton SQLContext object
that can be shared across
* the JVM.
+ *
+ * If there an active SQLContext for current thread, it will returned
instead of the global one.
*/
def getOrCreate(sparkContext: SparkContext): SQLContext = {
+ val ctx = activeContexts.get()
+ if (ctx != null) {
+ return ctx
+ }
+
INSTANTIATION_LOCK.synchronized {
- if (lastInstantiatedContext.get() == null) {
+ val ctx = instantiatedContext.get()
+ if (ctx == null) {
new SQLContext(sparkContext)
+ } else {
+ ctx
}
}
- lastInstantiatedContext.get()
}
- private[sql] def clearLastInstantiatedContext(): Unit = {
+ private[sql] def clearInstantiatedContext(): Unit = {
+ INSTANTIATION_LOCK.synchronized {
+ instantiatedContext.set(null)
+ }
+ }
+
+ private[sql] def clearTheInstantiatedContext(sqlContext: SQLContext):
Unit = {
INSTANTIATION_LOCK.synchronized {
- lastInstantiatedContext.set(null)
+ instantiatedContext.compareAndSet(sqlContext, null)
}
}
- private[sql] def setLastInstantiatedContext(sqlContext: SQLContext):
Unit = {
+ private[sql] def setInstantiatedContext(sqlContext: SQLContext): Unit = {
INSTANTIATION_LOCK.synchronized {
- lastInstantiatedContext.set(sqlContext)
+ instantiatedContext.compareAndSet(null, sqlContext)
}
}
+ /*
+ * Set a SQLContext for current thread
--- End diff --
"Changes the SQLContext that will be returned in this thread and its
children when `SQLContext.getOrCreate()` is called. This can be used to ensure
that a given thread receives a SQLContext with an isolated session, instead of
the global (first created) context."
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